The present invention relates to platinum group metal catalyzed addition-curable silicone adhesive compositions employing a bis(trialkoxysilylalkylene)amine or urea as an adhesion promoter.
As shown by Schulz, U.S. Pat. No. 4,087,585, the adhesion of a cured platinum catalyzed addition-curable silicone composition applied onto a substrate is achieved by effecting the cure of the silicone composition at a temperature such as 150.degree. C. An epoxysilane is used as an adhesion promoter. Although improved adhesion is achieved on metallic substrates as compared to employing the same silicone composition free of adhesion promoter, it is reported by Kasuya in U.S. Pat. No. 4,980,413, that the adhesive compositions of Schulz exhibit poor adhesion to plastic substrates.
Mitchell et al, U.S. Pat. No. 5,164,461, which is incorporated herein by reference, is directed to the use of certain silylmaleates, silylmaleimides or silylfumarates, such as bis[3-(trimethoxysilyl)alkyl]fumarates as adhesion promoters in addition-curable silicone adhesive compositions. Although the addition-curable silicone compositions of Mitchell et al have been found to be self-bonding to various substrates, such as plastics, metals or glass, these silicone adhesive compositions also require a temperature of about 100.degree. C. to about 150.degree. C. to effect a satisfactory cure.
It would be desirable therefore to provide other addition-curable silicone adhesive composition which could be applied onto an unprimed substrate, such as plastic or metal to effect a satisfactory cure in about an hour and at a temperature of about 100.degree. C. In addition, it also would be desirable to produce from such addition-curable silicone adhesive compositions, silicone substrate composites having a silicone layer which failed cohesively instead of adhesively when tested. As used hereinafter, the expression "adhesive failure" means the silicone layer can be cleanly separated from the substrate, while in a "cohesive failure" rupture occurs in the silicone layer or in the substrate when separation is achieved.